Sutures are widely used for repair of tissue in the human body. For sutures to function as intended, they must have good tensile strength and exhibit non-slip properties. In many instances, they must also have acceptable knot-tying and knot-holding characteristics.
Sutures can be made from a variety of materials including, for example, polypropylene, polyester, polyamide, polyglycolide and polylactide. Further, ultra-high molecular weight polyethylene (UHMWPE) is a common material growing in popularity, particularly for sutures that must exhibit strength, such as those used for orthopedic procedures. A suture filament is manufactured by braiding strands together. Strands can be monofilaments or multifilaments. Monofilaments are known for their smooth, uniform surface. Such properties provide advantages including reduced tissue drag. However, monofilaments are disadvantageous relative to multifilaments in that they are generally stiff, difficult to tie and are less adept in their ability to secure a knot. Multifilament strands are typically manufactured into a substantially cylindrically shaped braid to form a suture, which can either be hollow or include a core. Individual multifilament strands are typically made by twisting individual fibers together. Although multifilament strands have advantages relative to monofilament strands, the type of fibers chosen for their performance characteristics can at the same time have an adverse impact in other ways. For example, using UHMWPE fibers can provide strength properties to the suture, but such fibers may also be prone to slippage.
Currently, obtaining a suture, also referred to as a filament, that possesses the strength properties obtained when using UHMWPE fibers while also obtaining the friction properties of polyester has required the braiding of individual, independent strands together to form a filament. However, such a braided construction might not properly distribute the benefits of each of the materials evenly throughout the resulting braided filament, and thus the performance properties shift in accordance with the relative change in the constitution of the filament. This problem is particularly apparent in orthopedic surgery, and in particular surgery involving use of filament structures under high levels of tension. For instance, the problem is particularly acute for ACL surgery. In such circumstances, obtaining the advantages of both UHMWPE and polyester, in a uniform and consistent manner throughout the filament, would be desirable.
Thus, there is a need for a suture, or braided filament, that can achieve concurrent improved performance respecting both strength and friction properties. At the same time, the filament should achieve such an improvement while also having the ability to function in a knotless fashion.